1. Field of the Invention
The present invention relates to a method of making a poly-V ribbed pulley and, more particularly to a method making a poly-V ribbed pulley for use with poly-V belts.
2. Discussion of the Background
Poly-V ribbed pullies are widely used in the driving system of automobile engines or electric motors. An example of this type method of making a poly-V ribbed pulley is disclosed in Japanese Patent Publication No. 58(1983)-54898. The method of making a poly-V ribbed pulley described therein comprises a press working process and a roll working process. The press working process is employed to form a cylinder having a bottom and two circular projections. Namely the cylinder having both the bottom and a flange at each end is made of a thick circular plate by press working wherein the thickness of the bottom becomes thinner than that of the flange. Afterwards the flange is bent parallel with the axis of the cylinder so as to extend it, and two circular projections are formed at each side of the extended cylinder member. The rolling process is employed to form V-shaped grooves at the outside surface of the extended cylinder member by roll working.